JP6537995B2 - Hydraulic system of work machine - Google Patents

Description

  The present invention relates to a hydraulic system of a working machine such as a backhoe.

Conventionally, as a hydraulic system of a working machine (backhoe), a technology disclosed in Patent Document 1 is known.
The work machine disclosed in Patent Document 1 includes a work device having a boom, an arm, and a bucket, and a travel device having a left travel device and a right travel device. The boom is driven by the boom cylinder, the arm is driven by the arm cylinder, and the bucket is driven by the bucket cylinder. The left travel device is driven by the left travel motor, and the right travel device is driven by the right travel motor.

The hydraulic system of this working apparatus includes a first control valve that controls the right traveling motor and the arm cylinder, a second control valve that controls the left traveling motor, the boom cylinder, and the bucket cylinder, and a first pump port and a second pump port. And a variable displacement hydraulic pump.
Further, this hydraulic system is capable of supplying the first control fluid passage that can supply the control fluid from the first pump port to the first control valve, and the supply of the hydraulic fluid from the second pump port to the second control valve. The second hydraulic fluid passage, the first transmission fluid passage to which the load pressure of the hydraulic actuator controlled by the first control valve is transmitted, and the second, to which the load pressure of the hydraulic actuator controlled by the second control valve is transmitted It has a transmission oil passage.

  In addition, this hydraulic system has a switching valve that can be switched between the joining position and the independent position. At the joining position, the first hydraulic fluid passage and the second hydraulic fluid passage communicate with each other, and the first transmission fluid passage communicates with the second transmission fluid passage. In the independent position, the communication between the first hydraulic fluid passage and the second hydraulic fluid passage is released, and the communication between the first transmission fluid passage and the second transmission fluid passage is released. When driving the work device, it becomes the merging position. When the traveling device is operated without driving the working device, it becomes an independent position.

  The hydraulic system further includes a first return circuit for returning the hydraulic oil in the first transmission oil passage to the tank, and a second return circuit for returning the hydraulic oil in the second transmission oil passage to the tank.

JP, 2013-2241, A

However, in the technique of Patent Document 1, at the junction position, the hydraulic oil of the first transmission oil passage and the second transmission oil passage is returned to the tank by the circuits of both the first return circuit and the second return circuit. . For this reason, the load pressure may be released too much, and the hydraulic pressure in the first transmission oil passage and the second transmission oil passage may not be easily boosted.
Then, an object of this invention is to provide the hydraulic system of the working machine which aimed at the improvement of the transmission of the load pressure of a hydraulic actuator.

A hydraulic system of a working machine according to an aspect of the present invention includes a first control valve that controls a hydraulic actuator, a second control valve that controls a hydraulic actuator, a tank that stores hydraulic fluid, and a hydraulic fluid. The first hydraulic fluid passage that can be supplied to the control valve, the second hydraulic fluid passage that can supply the hydraulic fluid to the second control valve, and the load pressure of the hydraulic actuator controlled by the first control valve are transmitted And the second hydraulic fluid passage to which the load pressure of the hydraulic actuator controlled by the second control valve is transmitted, and the first hydraulic fluid passage and the second hydraulic fluid passage. And a junction position connecting the first transmission oil passage and the second transmission oil passage, and releasing the communication between the first hydraulic oil passage and the second hydraulic oil passage, and the first transmission oil passage A first switch that can be switched to an independent position for releasing communication with the second transmission oil passage A valve and a circuit connected to the first transmission oil passage at the independent position to return hydraulic oil of the first transmission oil passage to the tank, the connection with the first transmission oil passage at the joining position A first return circuit for releasing
And a second return circuit for returning hydraulic oil in the transmission oil path to the tank.

  According to the hydraulic system of the work machine, since the first return circuit is disconnected from the first transmission oil passage at the joining position, the first transmission oil passage and the second transmission oil passage are connected. Sometimes, only the second return circuit functions as a return circuit for returning the hydraulic oil of the first transmission oil passage and the second transmission oil passage to the tank. Therefore, the load pressure in the first transmission oil passage and the second transmission oil passage is favorably boosted without returning too much hydraulic oil of the first transmission oil passage and the second transmission oil passage to the tank.

It is the schematic of an oil path system. It is an oil-path circuit diagram of a control valve. It is an oil-path circuit diagram of a part of control valve. It is an oil-path circuit diagram of a part of control valve. FIG. 6 is an oil passage circuit diagram showing a joining position. It is an oil-path circuit diagram which shows an independent position. It is an oil-path circuit diagram which shows a part of oil-path system. It is a side view which shows the whole structure of a working machine.

Hereinafter, a preferred embodiment of a working machine according to the present invention will be described with reference to the drawings as appropriate.
FIG. 8 is a schematic side view showing the overall configuration of the work machine 1 according to the present embodiment. In the present embodiment, a backhoe which is a turning work machine is illustrated as the work machine 1.
<Overall configuration of work machine>
First, the overall configuration of the work machine 1 will be described.

As shown in FIG. 8, the work machine 1 includes a machine body (pivot table) 2, a traveling device 3, and a work device 4. A cabin 5 is mounted on the fuselage 2. A driver's seat 6 is provided in the cabin 5.
In the embodiment of the present invention, the front side (left side in FIG. 8) of the driver sitting on the driver's seat 6 of the work machine 1 is forward, the rear side (right side in FIG. 8) of the driver is rear, and the left side The front side of 8) is described as the left, and the right side of the driver (the rear side in FIG. 8) is described as the right. Further, a horizontal direction which is a direction orthogonal to the front-rear direction K1 will be described as the machine width direction.

  As shown in FIG. 8, the traveling device 3 has a first traveling device 3L provided on the left side of the frame of the traveling device 3 and a second traveling device 3R provided on the right side of the frame. In other words, the first traveling device 3L is provided on the left side of the lower part of the vehicle body 2. The second traveling device 3 </ b> R is provided on the right side of the lower part of the vehicle body 2. In the present embodiment, the first traveling device 3L and the second traveling device 3R are configured by crawler traveling devices. The first traveling device 3L is driven by a first traveling motor M1. The second travel device 3R is driven by a second travel motor M2 different from the first travel motor M1. The first traveling motor M1 and the second traveling motor M2 are configured by hydraulic motors (hydraulic actuators).

At the front of the traveling device 3, a dozer device 7 is mounted. The dozer device 7 can raise and lower (raise and lower the blade) by expanding and contracting the dozer cylinder C1.
The airframe 2 is pivotably supported on a frame of the traveling device 3 via a pivot bearing 8 about a longitudinal axis (an axis extending in the vertical direction). The airframe 2 is rotationally driven by a swing motor M3 formed of a hydraulic motor (hydraulic actuator). The airframe 2 has a substrate (hereinafter referred to as a pivoting substrate) 9 which pivots about the longitudinal axis, and a weight 10. The pivoting substrate 9 is formed of a steel plate or the like and is connected to the pivoting bearing 8. The weight 10 is provided at the rear of the airframe 2. At the rear of the fuselage 2, an engine E1 is mounted.

The airframe 2 has a support bracket 13 at the front slightly to the right of the center in the width direction of the airframe. A swing bracket 14 is attached to the support bracket 13 so as to be pivotable about a longitudinal axis. The work device 4 is attached to the swing bracket 14.
As shown in FIG. 8, the working device 4 has a boom 15, an arm 16 and a bucket (working tool) 17. The base of the boom 15 is pivotally attached to the swing bracket 14 so as to be rotatable about a lateral axis (axis in the machine width direction). Thus, the boom 15 is pivotable up and down. The arm 16 is pivotally mounted on the distal end side of the boom 15 about a lateral axis. By this, the arm 16 is made swingable back and forth or up and down. The bucket 17 is provided on the tip end side of the arm 16 so as to be able to perform a squeeze operation and a dumping operation. The work machine 1 can mount other work (hydraulic attachment) that can be driven by a hydraulic actuator, instead of or in addition to the bucket 17. As other working tools, a hydraulic breaker, a hydraulic crusher, an angle bloom, an earth auger, a pallet fork, a sweeper, a mower, a snow blower, etc. can be exemplified.

  The swing bracket 14 is swingable by expansion and contraction of a swing cylinder C2 provided in the machine body 2. The boom 15 is swingable by extension and contraction of the boom cylinder C3. The arm 16 is pivotable by extension and contraction of the arm cylinder C4. The bucket 17 is movable in a squeeze operation and a dumping operation by expansion and contraction of a bucket cylinder (work implement cylinder) C5. The dozer cylinder C1, the swing cylinder C2, the boom cylinder C3, the arm cylinder C4, and the bucket cylinder C5 are constituted by hydraulic cylinders (hydraulic actuators).

The boom 15 may be of a two-piece design. The two-piece design is a specification in which the boom 15 is configured by two members of a front boom and a rear boom, and can be bent at the connection portion of the front boom and the rear boom. In the case of the two-piece type, in addition to the boom cylinder C3, a second boom cylinder for performing an operation of bending the boom 15 at the connection portion is additionally mounted.
<Hydraulic system>
Next, referring to FIGS. 1 to 7, a hydraulic system (hydraulic system of a working machine) for operating various hydraulic actuators M1 to 3 and C1 to 5 equipped to the working machine 1 and hydraulic actuators separately equipped. Will be explained.

As shown in FIG. 1, the hydraulic system has a control valve CV1, a pressure oil supply unit SU1, and a tank T1 for storing oil for hydraulic pressure. The hydraulic oil stored in the tank T1 is used to drive a hydraulic actuator, for control, or for signaling. For convenience of explanation, hydraulic oil used for control or signal is referred to as "pilot oil", and pressure of pilot oil is referred to as "pilot pressure". Also, hydraulic oil may be referred to as "pressure oil".
The hydraulic system employs a load sensing system.

  The load sensing system functions as load adjustment between the hydraulic actuators M1 to 3 and C1 to 5 when a plurality of hydraulic actuators M1 to 3 and C1 to 5 equipped to the work machine 1 are operated at the same time. Pressure compensation valves E1 to E11 to be described later function as adjustment), and a pressure loss corresponding to the maximum load pressure is generated in the low load pressure side control valve V1 to 11, regardless of the load size, the control valve It is a system capable of flowing (distributing) a flow rate corresponding to an operation amount for operating V1 to 11 to the operated control valves V1 to 11.

In addition, the load sensing system controls the discharge amount of the hydraulic fluid discharged from the first pump 27 described later according to the load pressure of each of the hydraulic actuators M1 to 3 and C1 to 5 installed in the work machine 1 (load sensing This is a system capable of saving power and improving operability by controlling the hydraulic pressure required for the load and discharging the hydraulic power from the first pump 27. <Overview of control valve>
The control valve CV1 is a valve unit in which a plurality of control valves V1 to V11, a plurality of end blocks B1 and B2, and a plurality of valve blocks B3 and B4 are arranged in one direction and arranged. Further, the control valve CV1 has a valve block B5 provided to the valve block B4.

  Control valves V1 to V11, end block B1, and valve blocks B3 and B4 are, from the right in FIG. 1, from the right, control valve V1, control valve V2, valve block B3, valve block B4, control valve V3, control valve V4, control valve V5, control valve V6, control valve V7, control valve V8, control valve V9, control valve V10, control valve V11, and end block B2 are arranged in this order and joined together.

The plurality of control valves V1 to V11 are valves for operating the various hydraulic actuators M1 to M3 and C1 to C5 equipped in the work machine 1 and hydraulic actuators separately equipped.
The control valve V1 is a first dozer valve that controls the dozer cylinder C1. The control valve V2 is a first travel valve that controls the first travel motor M1. The control valve V3 is a second travel valve that controls the second travel motor M2. The control valve V4 is a valve that controls the dozer cylinder C1, and is a second dozer valve different from the control valve V1. The control valve V5 is a first spare valve that controls a hydraulic attachment that is separately mounted. The control valve V6 is an arm valve that controls the arm cylinder C4. The control valve V7 is a bucket valve (work implement valve) that controls the bucket cylinder C5. The control valve V8 is a boom valve that controls the boom cylinder C3. The control valve V9 is a swing valve that controls the swing motor M3. The control valve V10 is a valve for controlling a hydraulic attachment that is separately mounted, and is a second spare valve different from the control valve V5. The control valve V11 is a swing valve that controls the swing cylinder C2.

The control valve V1 and the control valve V2 constitute a first control valve. That is, the first control valve is a valve that controls the hydraulic actuator (the dozer cylinder C1, the first traveling motor M1). In addition, the first control valve includes at least a first travel valve V2, and in the present embodiment, also includes a first dozer valve V1.
The control valves V3 to V11 constitute a second control valve. That is, the second control valve is a valve that controls the hydraulic actuator (the second travel motor M2, the dozer cylinder C1, the hydraulic attachment, the arm cylinder C4, the bucket cylinder C5, the boom cylinder C3, the swing motor M3, the swing cylinder C2) . The second control valve includes at least a second travel valve V3. In the present embodiment, the second dozer valve V4, the first spare valve V5, the arm valve V6, the bucket valve V7, the boom valve V8, the turning valve V9, It also includes a second preliminary valve V10 and a swing valve V11.

The first spare valve V5, the arm valve V6, the bucket valve V7, the boom valve V8, the swing valve V9, the second spare valve V10, and the swing valve V11 are provided in either the first control valve or the second control valve. It should just be.
The control valve CV1 has input ports 18 to 22 and output ports 23 and 24. The input port 18 and the input port 19 are ports to which hydraulic oil discharged from a first pump 27 described later is input, and are provided in the valve block B5. The input port 20 is provided in the end block B1. The input port 21 is provided in the end block B2. The input port 22 is provided in the valve block B4. The output port 23 and the output port 24 are provided in the valve block B3. The output port 23 is a port that outputs a PLS signal pressure (PLS: Pressure of Load Sensing), which is the maximum load pressure among the various hydraulic actuators M1 to 3 and C1 to C5. The output port 24 is a port that outputs a PPS signal pressure (PPS: Pressure of Pump Sensing) that is a discharge pressure of the first pump 27.
<Pressure oil supply unit>
The pressure oil supply unit SU1 has a unit body 26, a first pump 27, a second pump 28, and a control unit 29. The first pump 27, the second pump 28, and the control unit 29 are incorporated in the unit body 26.

The first pump 27 is a hydraulic pump that sucks the oil in the tank T1 and discharges (supplys the hydraulic fluid) hydraulic fluid that operates the various hydraulic actuators M1 to M3 and C1 to C5. The second pump 28 is a hydraulic pump that discharges pilot oil. The first pump 27 and the second pump 28 are driven by the engine E1.
The first pump 27 is a hydraulic pump having the function of an equal flow rate double pump that discharges an equal amount of pressure oil (hydraulic oil) from two independent discharge ports, and is a swash plate type variable displacement axial that can vary the displacement. It consists of a pump. More specifically, the first pump 27 employs a split flow hydraulic pump having a mechanism for alternately discharging pressure oil from one piston and cylinder barrel kit to discharge grooves formed in and out of the valve plate.

  Of the two discharge ports from which hydraulic fluid is discharged from the first pump 27, one discharge port is referred to as a first pump port P1, and the other discharge port is referred to as a second pump port P2. The first pump 27 may be configured by two independent hydraulic pumps. In this case, the discharge port of one of the two hydraulic pumps is the first pump port, and the discharge port of the other hydraulic pump is the second pump port.

The second pump 28 is configured by a fixed displacement gear pump. The second pump 28 is a hydraulic pump that sucks the oil in the tank T1 and discharges the pilot oil.
The unit body 26 is provided with output ports 30 to 32 and input ports 33 to 35. The output port 30 outputs the hydraulic oil discharged from the first pump port P1. The output port 30 is connected to the input port 18 via the supply oil passage 36. The output port 31 outputs the hydraulic oil discharged from the second pump port P2. The output port 31 is connected to the input port 19 via the supply oil passage 37. The output port 32 outputs the hydraulic oil discharged from the second pump 28. The output port 32 is connected to the input port 20 via the supply oil passage 38 and the supply oil passage 39. Further, the output port 32 is connected to the input port 21 via the supply oil passage 38, the supply oil passage 40, and the supply oil passage 41. Further, the output port 32 is connected to the input port 22 via the supply oil passage 38, the supply oil passage 39, and the supply oil passage 58. Further, the output port 32 is connected to the input port 35 via the supply oil passage 38, the supply oil passage 40, and the supply oil passage 42. The input port 33 is connected to the output port 24 via a signal oil path (PPS signal oil path) 47. That is, the PPS signal pressure is input to the input port 33. The input port 34 is connected to the output port 23 via a signal oil path (PLS signal oil path) 48. That is, the PLS signal pressure is input to the input port 34.

The control unit 29 is a device that controls the flow rate of the hydraulic oil discharged from the first pump 27. In other words, the flow rate control unit 29 is a device that performs swash plate control of the first pump 27.
The control unit 29 has a pressing device 43 for pressing a swash plate of the first pump 27 and a swash plate control device 44 for flow rate compensation for controlling the swash plate of the first pump 27. The first pump 27 is configured such that the swash plate is pressed in the direction of increasing the pump flow rate through the pressing device 43 by the self pressure of the first pump 27. Further, a force against the pressing force of the pressing device 43 is applied to the swash plate by the swash plate control device 44. By controlling the pressure acting on the swash plate control device 44, the discharge flow rate of the first pump 27 is controlled.

When the pressure acting on the control piston 44 is released, the first pump 27 discharges the maximum flow rate with the swash plate angle MAX.
Further, the control unit 29 has a control valve V12 for flow rate compensation. By controlling the pressure acting on the swash plate control device 44 by the control valve V12, the swash plate control of the first pump 27 is performed.

  An input port 33 is connected to one side of the spool of the control valve V12 via an oil passage 49. That is, the discharge pressure (PPS signal pressure) of the first pump 27 acts on one end side of the spool of the control valve V12. Further, an input port 34 is connected to the other side of the spool of the control valve V12 via an oil passage 50. That is, the maximum load pressure (PLS signal pressure) of the hydraulic actuator acts on the other end side of the spool of the control valve V12. Further, on the other end side of the spool of the control valve V12, a spring 51 for giving a control differential pressure to the control valve V12 and a differential pressure cylinder 52 are provided.

The control valve V12 controls the swash plate control device 43 based on the PLS signal pressure and the PPS signal pressure. The swash plate control device 43 sets the first pump 27 so that the pressure difference between the PPS signal pressure and the PLS signal pressure becomes the control differential pressure (so that the difference between the PPS signal pressure and the PLS signal pressure is maintained at the set value). Automatic control (load sensing control) of the discharge flow rate (discharge pressure) of
That is, the hydraulic system (load sensing system) includes the first pump port P1 and the second pump port based on the discharge pressure of the first pump 27 (the first pump port P1 or the second pump port P2) and the load pressure of the hydraulic actuator. A controller 29 is provided to control the flow rate of hydraulic fluid discharged from P2.

Further, the control unit 29 is provided with a spring 45 for controlling the pump horsepower (torque) of the first pump 27 and a spool 46. The spring 45 and the spool 46 are configured to limit the horsepower (torque) that the first pump 27 absorbs from the engine E1 when the discharge pressure of the first pump 27 reaches a preset pressure.
Next, details of the control valve CV1 will be described.

As shown in FIGS. 2 to 4, the control valves V1 to V11 incorporate direction switching valves D1 to D11 and pressure compensation valves E1 to E11 in the valve body.
The direction switching valves D1 to D11 are valves that switch the direction of pressure oil to the hydraulic actuators M1 to M3 and C1 to C5 to be controlled. The directional control valves D1 to D11 are direct-acting spool type three-position control valves. The direction switching valves D1 to D11 are pilot (operation) switching valves that are switched by a pilot pressure (pilot oil). The spools of the direction switching valves D1 to D11 constitute a main spool of the control valves V1 to V11. Therefore, the control valves V1 to V11 can be said to be pilot (operation) switching valves that are switched by the pilot pressure. Further, in the direction switching valves D1 to D11, the spools are moved in proportion to the operation amount of the operating device that operates the direction switching valves D1 to D11. The pressure oil in an amount proportional to the moved amount of the spool is supplied to the hydraulic actuators M1 to M3 and C1 to C5 to be controlled (the operation is performed in proportion to the operation amount of each operation device The operating speeds of the target hydraulic actuators M1 to M3 and C1 to C5 can be changed).

  The pressure compensation valves E1 to E11 are disposed downstream of the pressure oil supply to the direction switching valves D1 to D11 and upstream of the pressure oil supplied to the hydraulic actuators M1 to M3 and C1 to C5 to be controlled. That is, the load sensing system of the present embodiment employs an after-orifice load sensing system in which the pressure compensation valves E1 to E11 are disposed downstream of the pressure oil supply with respect to the direction switching valves D1 to D11.

The pressure compensating valves E1 to E11 function as load adjustment among the hydraulic actuators M1 to M3 and C1 to C5 when a plurality of hydraulic actuators M1 to M3 and C1 to C5 are simultaneously operated, and the control valve on the low load pressure side A pressure loss corresponding to the differential pressure with the maximum load pressure is generated in V1 to V11, and a flow corresponding to the operation amount of the spool of the direction switching valve D1 to D11 is allowed to flow (distributed) regardless of the size of the load it can.
<Air venting circuit for pilot oil passage of dozer valve>
As shown in FIG. 3, the hydraulic system includes a remote control valve (operating device) 56 that operates the dozer device 7. The remote control valve 56 has a dozer lever (operation member) 56A. Further, the remote control valve 56 is provided in the vicinity of the driver's seat 6. The remote control valve 56 is a pilot valve that pilots the control valve V1 (first dozer valve) and the control valve V4 (second dozer valve) by operating the dozer lever 56A. Further, the remote control valve 56 simultaneously outputs pilot oil to the direction switching valve D1 and the direction switching valve D4 by operating the dozer lever 56A. As a result, the direction switching valve D1 and the direction switching valve D4 are simultaneously operated (simultaneously operated). Hereinafter, for convenience of description, the direction switching valve D1 may be referred to as a "first pilot switching valve", and the direction switching valve D4 may be referred to as a "second pilot switching valve".

  The hydraulic system includes a pilot circuit 53 that supplies pilot oil from the remote control valve 56 to the control valve V1 (first pilot switching valve D1) and the control valve V4 (second pilot switching valve D4). The pilot circuit 53 is a circuit for supplying, from the remote control valve 56, pilot oil for switching instruction to switch the direction switching valve D1 and the direction switching valve D4 to the control valve V1 and the control valve V4. That is, the pilot circuit 53 constitutes a hydraulic oil flow path through which the pilot oil supplied from the remote control valve 56 (operation device) to the first pilot switching valve D1 and the second pilot switching valve D4 flows.

The pilot circuit 53 has a first supply circuit 54 that supplies pilot oil to the control valve V1, and a second supply circuit 55 that supplies pilot oil to the control valve V4. The first supply circuit 54 has a first pilot oil passage 54A and a second pilot oil passage 54B. The second supply circuit 55 includes a third pilot oil passage 55A and a fourth pilot oil passage 55B.
One end of the first pilot oil passage 54A is connected to the remote control valve 56, and the other end is connected to the pressure receiving portion (first pressure receiving portion) 57A of the direction switching valve D1. One end of the second pilot oil passage 54B is connected to the remote control valve 56, and the other end is connected to the pressure receiving portion (second pressure receiving portion) 57B of the direction switching valve D1. One end of the third pilot oil passage 55A is connected to the first pilot oil passage 54A, and the other end is connected to the pressure receiving portion (third pressure receiving portion) 57C of the direction switching valve D4. One end of the fourth pilot oil passage 55B is connected to the second pilot oil passage 54B, and the other end is connected to the pressure receiving portion (fourth pressure receiving portion) 57D of the direction switching valve D4. In the present embodiment, the first supply circuit 54 is a circuit that supplies pilot oil from the remote control valve 56 (operation device) to the first pilot switching valve D1. The second supply circuit 55 is a circuit that supplies pilot oil from the first supply circuit 54 to the second pilot switching valve D4. The first supply circuit 54 supplies pilot oil from the remote control valve 56 to the second pilot switching valve D4, and the second supply circuit 55 supplies pilot oil from the first supply circuit 55 to the first pilot switching valve D1. It may be a circuit that That is, the pilot circuit 53 supplies the pilot oil from the controller 56 to one of the first pilot switching valve D1 and the second pilot switching valve D4, and the first pilot switching valve from the first supply circuit 54. And D1 or a second supply circuit 55 for supplying a pilot oil to the other of the second pilot switching valve D4.

  In the present embodiment, when the dozer lever 56A is swung forward, the pilot pressure acts on the first pressure receiving portion 57A through the first pilot oil passage 54A and the third pressure receiving portion 57C through the third pilot oil passage 55A. The pilot pressure acts. As a result, the direction switching valve D1 and the direction switching valve D4 are switched in the direction in which the dozer device 7 operates to raise. In addition, when the dozer lever 56A is swung rearward, the pilot pressure acts on the second pressure receiving portion 57B through the second pilot oil passage 54B, and the pilot pressure is received by the fourth pressure receiving portion 57D through the fourth pilot oil passage 55B. Works. As a result, the direction switching valve D1 and the direction switching valve D4 are switched in the direction in which the dozer device 7 operates downward.

  Further, of the control valve V1 (first pilot switching valve D1) and the control valve V4 (second pilot switching valve D4), the control valve V4 is provided with an air vent circuit 59, and the control valve V1 is vented. No circuit is provided. That is, the air vent circuit 59 is an air vent circuit 59 common to the first pilot switching valve D1 and the second pilot switching valve D4 (for a plurality of pilot switching valves). Further, control valve 4 on the downstream side of the oil flow path through which pilot oil for switching command switches the direction switching valve (first pilot switching valve) D1 and the direction switching valve (second pilot switching valve) D4 (pilot switching valve D4 ) Is provided with an air vent circuit 59. In other words, the air vent circuit 59 is provided downstream of the oil flow path for flowing the pilot oil supplied from the operation device 56 (of the plurality of pilot switching valves) of the first pilot switching valve D1 or the second pilot switching valve D2. It is provided on the side of the pilot switching valve side.

The air vent circuit 59 is not limited to the downstream side of the oil flow path of the pilot oil, and may be provided on the upstream side of the oil flow path of the pilot oil. That is, it may be provided in one of the control valve V1 (first pilot switching valve D1) and the control valve V4 (second pilot switching valve D2).
Air may be mixed in the pilot oil passages 54A, 54B, 55A, 55B when assembling hydraulic pressure distribution members such as hydraulic hoses constituting the pilot oil passages 54A, 54B, 55A, 55B. In addition, when oil (hydraulic oil) stagnates in pilot oil passages 54A, 54B, 55A, 55B when control valves V1, V2 are not used, etc., gas contained in oil may be precipitated as fine bubbles. is there. If air is present in the pilot oil passages 54A, 54B, 55A, 55B, the movement of the dozer cylinder C1 (hydraulic actuator) will deteriorate. The air removal circuit 59 is a circuit for removing air (bubbles) in the pilot oil passages 54A, 54B, 55A, 55B by returning the pilot oil in the pilot oil passages 54A, 54B, 55A, 55B to the tank T1.

  The air vent circuit 59 has a first relief passage 59A, a second relief passage 59B, a first throttle 59C, and a second throttle 59D. One end of the first escape passage 59A is connected to the third pilot oil passage 55A, and the other end is connected to the drain oil passage 60. One end of the first relief path 59A is connected to the vicinity of the pressure receiving portion 57C. One end of the second escape passage 59B is connected to the fourth pilot oil passage 55B, and the other end is connected to the first escape passage 59A. One end of the second escape path 59B is connected to the vicinity of the pressure receiving portion 57D.

The first throttle 59C is provided in the first escape passage 59A. The first throttle 59C may be provided in the vicinity of the connection between the third pilot oil passage 55A and the first relief passage 59A. The second throttle 59D is provided in the second escape passage 59B. The second throttle 59D may be provided in the vicinity of the connection between the fourth pilot oil passage 55B and the second relief passage 59B.
The drain oil passage 60 is provided in the control valve CV1, and reaches the end block B1 from the end block B3 through the control valves V11 to V1 and the valve blocks B4 and B3. The drain oil passage 60 communicates with the tank T1 via the relief valve V22 at the end block B1. Further, the drain oil passage 60 is in communication with the tank T1 via the oil passage 61 at the control valve V8.

When the pilot oil flows in the pilot oil passages 54A, 54B, 55A, 55B, part of the pilot oil flows through the first throttle 59C or the second throttle 59B into the drain oil passage 60 and is returned to the tank T1. As a result, when air is present in the pilot oil passages 54A, 54B, 55A, 55B, the air is discharged.
If both the control valve V1 (the first pilot switching valve D1) and the control valve V4 (the second pilot switching valve D2) are provided with an air venting circuit, the amount of leakage of the pilot oil will increase, and the pilot oil passage 54A, It may be difficult for 54B, 55A, 55B to step up. If the pilot oil passages 54A, 54B, 55A, 55B are not sufficiently boosted in pressure, the operating speed of the dozer device 7 becomes slow without pushing the spools of the direction switching valves D1, D4. By providing an air vent circuit 59 in one of the control valve V1 (first dozer valve) and the control valve V4 (second dozer valve), the air in the pilot oil passages 54A, 54B, 55A, 55B can be appropriately set. The pilot oil passages 54, 54B, 55A, 55B can be sufficiently pressurized and the operation speed of the dozer device 7 can be made appropriate while being removed.

  Further, when providing the air venting circuit 59 on one of the control valve V1 (first pilot switching valve D1) and the control valve V4 (second pilot switching valve D2), the air venting circuit 59 is provided on the control valve V4. There is. That is, the air vent circuit 59 is provided on the control valve 4 on the downstream side of the oil flow path in which the pilot oil for switching instruction for switching the direction switching valve D1 and the direction switching valve D4 flows. As a result, the air present on the upstream side in the pilot oil passages 54A, 54B, 55A, 55B can also be favorably removed. That is, the air can be satisfactorily removed (the air release property can be secured).

  In the present embodiment, although the air vent circuit is provided in one of the two control valves for the dozer device, it is not limited to the dozer device. In short, in a hydraulic system in which the same target (one) hydraulic actuator is controlled by a plurality of pilot switching valves simultaneously piloted, a common air vent circuit may be provided for the plurality of pilot switching valves. .

Further, in the present embodiment, the first pilot switching valve is provided in the valve body of the first control valve, and the second pilot switching valve is provided in the valve body of the second control valve. However, the present invention is not limited thereto. A plurality of piloted pilot valves may be assembled in one valve body, and a common air bleeding circuit may be provided for the plurality of pilot piloted valves.
<Load pressure return circuit for load sensing system>
As shown in FIG. 2, FIG. 3 and FIG. 4, the first relief valve V <b> 21 is incorporated in the end block B <b> 1. A first shuttle valve V14, a second shuttle valve V15, a first unload valve V18, and a second unload valve V19 are incorporated in the valve block B3. The valve block B4 incorporates a first switching valve V13, a second switching valve V20, a second relief valve V17, and a first return circuit 66. A bypass valve V16 is incorporated in the valve block B5. A second return circuit 67 is incorporated in the end block B2.

  The control valve CV1 has a first hydraulic fluid passage 68 through which hydraulic fluid from the first pump port P1 flows and a second hydraulic fluid passage 69 through which hydraulic fluid from the second pump port P2 flows. One end of the first hydraulic fluid passage 69 is connected to the input port 18. The first hydraulic fluid passage 68 passes through the valve block B5 and enters the valve block B4, and from B4 to the control block V2 and the control valve V1 to the end block B1. The other end of the first hydraulic fluid passage 68 is connected to the drain fluid passage 60 in the end block B1. Further, in the end block B1, the first hydraulic oil passage 68 is provided with a first relief valve V21. The first relief valve V21 is a variable relief valve capable of changing the set pressure to a first set pressure and a second set pressure which is a set pressure higher than the first set pressure. Further, in the present embodiment, the first relief valve V21 is a pilot actuated variable relief valve whose set pressure is changed by the pilot pressure.

As shown in FIGS. 5 and 6, the first relief valve V <b> 21 has a pressure receiving portion 64 and a setting spring 65. When the pilot pressure does not act on the pressure receiving portion 64, the first relief valve V21 has the first set pressure set by the set spring 65. In addition, when the pilot pressure acts on the pressure receiving portion 64, the pressure is changed to the second set pressure.
As shown in FIG. 2, FIG. 3 and FIG. 4, the first hydraulic fluid passage 68 is connected to the directional control valves D1 and D2 by respective fluid passages, and from the first hydraulic fluid passage 68 to the directional switching valves D1 and D2. It is possible to supply hydraulic oil to

  One end of the second hydraulic oil passage 69 is connected to the input port 19. The second hydraulic fluid passage 69 passes through the valve block B5 to enter the valve block B4, and from B4 to the control valve V11 via the control valves V3 to V10. The other end of the second hydraulic fluid passage 69 is closed. The second hydraulic fluid passage 69 is connected to the directional control valves D3 to D11 by respective fluid passages, so that hydraulic fluid can be supplied from the second hydraulic fluid passage 69 to the directional control valves D3 to D11.

  The bypass valve V16 is a direct acting spool type three-position switching valve operated by a pilot pressure. The bypass valve V16 is provided in the oil passage 104 and the oil passage 105 that connect the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 in parallel. The bypass valve V16 has a blocking position (neutral position) 106 for blocking the pressure oil flow in the oil passage 104 and the oil passage 105, and a first position 107 for permitting the pressure oil in the oil passage 104 and blocking the oil passage 105. And the second position 104 which shuts off the oil passage 104 and allows the pressure oil to flow in the oil passage 105.

  A pilot pressure output from an operating valve (operating device) V26 operating the control valve V3 acts to switch the bypass valve V16 from the shutoff position 106 to the first position 107. Further, the pilot pressure output from the operating valve (operating device) V27 operating the control valve V2 acts to switch the bypass valve V16 from the shutoff position 106 to the second position 108. Further, when a pressure difference between the control valve V26 and the control valve V27 generates a differential pressure equal to or greater than a predetermined pressure, the bypass valve V16 is switched from the cutoff position 106 to the first position 107 or the second position 108 by the pilot pressure on the high pressure side. Can be switched to

The first hydraulic fluid passage 68 is connected to the first switching valve V13 by a first connection fluid passage 71. The second hydraulic oil passage 69 is connected to the first switching valve V13 by a second connection oil passage 72.
Further, the first hydraulic fluid passage 68 is connected to one input port of the first shuttle valve V14 by a signal fluid passage 79, and the hydraulic fluid of the first hydraulic fluid passage 68 is inputted to the first shuttle valve V14. The second hydraulic fluid passage 69 is connected to the other input port of the first shuttle valve V14 via the second connection fluid passage 72 and the signal fluid passage 80, and the hydraulic fluid of the second hydraulic fluid passage 69 is the first shuttle valve. It is input to V14. The first shuttle valve V14 outputs, from the output port, the hydraulic oil having the higher pressure among the hydraulic oil input from the input port (in the case of the same pressure, the hydraulic oil from the open side input port is output) ). The output port of the first shuttle valve V14 is connected to the output port 24. As a result, the PPS signal pressure (the discharge pressure of the first pump port P1 and the second pump port P2) is output from the output port 24.

  Further, the signal oil passage 79 is connected to the first unloading valve V18 via an oil passage 86. The signal oil passage 80 is connected to the second unloading valve V19 via an oil passage 87. The first unloading valve V18 is biased in the closing direction by the biasing force of the spring and acts in the direction in which the oil passage 86 closes. The second unloading valve V19 is biased in the closing direction by the biasing force of the spring and acts in the direction in which the oil passage 87 closes.

The first switching valve V13 is a direct acting spool type two-position switching valve. Further, the first switching valve V13 is a pilot operation switching valve that is switched by the pilot pressure.
As shown to FIG. 5, FIG. 6, the 1st switching valve V13 has six ports 73a-73f. The first connection oil passage 71 is connected to the port 73a. The second connection oil passage 72 is connected to the port 73 b. One end of a first transmission oil passage 74 is connected to the port 73 c. One end of a second transmission oil passage 75 is connected to the port 73 d. One end of a relief oil passage 76 is connected to the port 73 e. One end of the oil discharge passage 77 is connected to the port 73 f.

  As shown in FIGS. 2 and 3, the first transmission oil passage 74 is provided from the valve block B4 to the control valve V1 through the control valve V2. The other end of the first transmission oil passage 74 is closed. In the first transmission oil passage 74, pressure compensation valves E1, E2 are connected via load transmission oil passages Y1, Y2. The load pressure of the hydraulic actuator (the dozer cylinder C1 and the first travel motor M1) to be controlled by the control valves V1 and V2 is transmitted to the first transmission oil passage 74 through the load transmission oil passages Y1 and Y2.

  As shown in FIGS. 2 and 4, the second transmission oil passage 75 passes from the valve block B4 to the end block B2 via the control valves V3 to V11. A second return circuit 67 is connected to the other end of the second transmission oil passage 75. The second return circuit 67 is connected to the drain oil passage 60 at the end block B2. Pressure compensating valves E3 to E11 are connected to the second transmission oil passage 75 via load transmission oil passages Y3 to Y11. The hydraulic actuators (the second travel motor M2, the dozer cylinder C1, the hydraulic attachment, the arm cylinder C4, the bucket cylinder C5, the boom cylinder C3, the turning motor M3 and the like) are controlled by the load transfer oil paths Y3 to Y11. , And the load pressure of the swing cylinder C2) is transmitted to the first transmission oil passage 74.

  The second return circuit 67 includes a connection oil passage (second connection oil passage) 67A, a throttle 67B, and an oil filter 67C. One end of the second connection oil passage 67A is connected to the other end of the second transmission oil passage 75, and the other end is connected to the drain oil passage 60. The throttle 67B and the oil filter 67C are provided in the second connection oil passage 67A. The throttle 67B is provided downstream of the oil filter 67C. The second return circuit 67 is a circuit for returning the pressure oil of the second transmission oil passage 75 to the tank T1.

  The relief oil passage 76 is provided with a second relief valve V17. The second relief valve V17 is a relief valve whose set pressure is determined by the set spring 91. The set pressure of the second relief valve V17 is the same set pressure as the second set pressure of the first relief valve V21. The other end of the relief oil passage 76 is connected to the drain oil passage 60 and is in communication with the tank T1.

The other end of the oil discharge passage 77 is connected to the relief oil passage 76 via an oil passage 78. Further, the other end of the oil discharge passage 77 is connected to the relief oil passage 76 downstream of the second relief valve V17. Thus, the oil discharge passage 77 communicates with the tank T1.
Further, the first transmission oil passage 74 is connected to one input port of the second shuttle valve V15 via the signal oil passage 81, and the pressure oil of the first transmission oil passage 74 is inputted to the second shuttle valve V15. . The second transmission oil passage 75 is connected to the other input port of the second shuttle valve V15 via the signal oil passage 82, and the pressure oil of the second transmission oil passage 75 is input to the second shuttle valve V15. The second shuttle valve V15 outputs the hydraulic oil having the higher pressure among the hydraulic oil input from the input port from the output port (in the case of the same pressure, the hydraulic oil from the open side input port is output) ). The output port of the second shuttle valve V15 is connected to the output port 23. As a result, the PLS signal pressure (maximum load pressure of the hydraulic actuator) is output from the output port 23.

As shown in FIGS. 3, 5 and 6, the first switching valve V <b> 13 is switchable between a joining position 83 and an independent position 84. The first switching valve V13 is biased by a spring 85 in a direction to be switched to the merging position 83.
When the first switching valve V13 is at the merging position 83 (see FIG. 5), the first connection oil passage 71 and the second connection oil passage 72 are connected. That is, the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 are communicated (connected) via the first connection fluid passage 71 and the second connection fluid passage 72. As a result, the discharge oil of the first pump port P1 and the discharge oil of the second pump port P2 are merged and can be supplied to the direction switching valves D1 to D11 of the control valves V1 to V11. Further, at the joining position 83, the first transmission oil passage 74 and the second transmission oil passage 75 are connected. That is, at the merging position 83, the first switching valve V13 merges the hydraulic oil from the first pump port P1 and the second pump port P2 so that it can be supplied to the first control valve and the second control valve, and the first transmission The oil passage 74 and the second transmission oil passage 75 are connected.

  When the first switching valve V13 is in the independent position 84 (see FIG. 6), the connection between the first connection oil passage 71 and the second connection oil passage 72 is released (blocked). That is, the communication between the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 is released. As a result, the discharge oil of the first pump port P1 can be supplied to the directional control valves D2 and D1 of the control valve (first travel valve valve) V2 and the control valve (first dozer valve) V1, and the second pump port The pressure oil from P2 can be supplied to the direction switching valves D3 and D4 of the control valve (second travel valve) V3 and the control valve (second dozer valve) V4. In the independent position 84, pressure oil from the second pump port P2 can be supplied to the direction switching valves D5 to D11 of the control valves V5 to V11.

Further, at the independent position 84, the connection between the first transmission oil passage 74 and the second transmission oil passage 75 is released. That is, in the independent position 84, the hydraulic oil from the first pump port P1 can be supplied to the first control valve, and the hydraulic oil from the second pump port P2 can be supplied independently to the second control valve, and the first transmission oil The communication between the passage 74 and the second transmission oil passage 75 is released.
As shown in FIGS. 5 and 6, the first switching valve V13 has a communication oil passage 88 and a first return circuit 66. The communicating oil passage 88 connects the port 73 b and the port 73 e at the independent position 84. As a result, the second connection oil passage 72 (the second hydraulic oil passage 69) and the relief oil passage 76 are connected at the independent position 84. Further, at the joining position 83, the communication oil passage 88 is disengaged from the port 73b and the port 73e (is disengaged from the second connection oil passage 72 and the relief oil passage 76). As a result, the connection between the port 73b and the port 73e by the communication oil passage 88 is released, and the connection between the second connection oil passage 72 (the second hydraulic oil passage 69) and the relief oil passage 76 is released.

The first return circuit 66 has a connection oil passage (first connection oil passage) 66A, a throttle 66B, and an oil filter 66C. The throttle 66B and the oil filter 66C are provided in the first connection oil passage 66A. The throttle 66B is provided downstream of the oil filter 66C.
The first connection oil passage 66A is provided on the spool of the first switching valve V13, and is formed, for example, in a groove or a hole formed in the first spool.

  In the independent position 84, one end of the first connection oil passage 66A is connected to the first transmission oil passage 74 (port 73c), and the other end of the first connection oil passage 66A is connected to the oil drainage passage 77 (port 73f) . That is, the first connection oil passage 66 </ b> A connects the first transmission oil passage 74 and the oil discharge passage 77 at the independent position 84. As a result, in the independent position 84, the first transmission oil passage 74 communicates with the tank T1 via the first connection oil passage 66A, the oil discharge passage 77, the oil passage 78, the relief oil passage 76, the drain oil passage 60 and the like. .

  Further, at the joining position 83, the first connection oil passage 66A is disengaged from the first transmission oil passage 74 (port 73c) and the oil discharge passage 77 (port 73f). That is, the first connection oil passage 66A releases the connection between the first transmission oil passage 74 and the oil discharge passage 77 at the joining position 83. In other words, at the joining position 83, the connection between the first transmission oil passage 74 and the oil discharge passage 77 by the first connection oil passage 66A (the first return circuit 66) is released.

The first return circuit 66 is a circuit connected to the first transmission oil passage 74 at the independent position 83 to return the pressure oil of the first transmission oil passage 74 to the tank T 1. It is a circuit to which the connection with is released.
Further, the second return circuit 67 is a circuit for returning the pressure oil of the second transmission oil passage 75 to the tank T1 at the joining position 83 and the independent position 84.

  Since the first return circuit 66 is disconnected from the first transmission oil passage 74 at the merging position 83, when the first transmission oil passage 74 and the second transmission oil passage 75 are connected, the second return circuit 66 performs the second return. Only the circuit 67 functions as a return circuit for returning the pressure oil in the first transmission oil passage 74 and the second transmission oil passage 75 to the tank T1. Therefore, the pressure oil in the first transmission oil passage 74 and the second transmission oil passage 75 is not returned too much to the tank T1, and the load pressure in the first transmission oil passage 74 and the second transmission oil passage 75 is well boosted. Do. As a result, when the first transmission oil passage 74 and the second transmission oil passage 75 are connected, flow control (load sensing control) of the discharge oil of the first pump 27 can be favorably performed.

  Further, since the first return circuit 66 is connected to the first transmission oil passage 74 at the independent position 84, when the communication between the first transmission oil passage 74 and the second transmission oil passage 75 is released, The pressure oil in the transmission oil passage 74 is returned to the tank T1 by the first return circuit 66, and the pressure oil in the second transmission oil passage 75 is returned to the tank T1 by the second return circuit 67. As a result, when the first transmission oil passage 74 and the second transmission oil passage 75 are shut off, flow control (load sensing control) of the discharge oil of the first pump 27 can be favorably performed.

Further, by providing the first return circuit 66 in the first switching valve V13, the first return circuit 66 can be easily configured, and the hydraulic circuit can be simplified.
As shown in FIGS. 3, 5 and 6, the first switching valve V13 is switched by the second switching valve V20. The second switching valve V20 is composed of a direct acting spool type two-position switching valve. Further, the second switching valve V20 is configured by a pilot operation switching valve that is switched by the pilot pressure.

  The second switching valve V20 has a release position 89 and a switching position 90. The second switching valve V20 is biased by a spring 92 in a direction to be switched to the release position 89. The second switching valve V20 is connected to the input port 22 via the supply oil passage 93, and can supply the discharge oil (pilot oil) discharged from the second pump 28 to the second switching valve V20. Further, the second switching valve V20 is connected to the pressure receiving portion 95 of the first switching valve V13 via the pilot oil passage 94. The pressure receiving unit 95 is a pressure receiving unit that applies a switching pressure (pilot pressure) that switches the first switching valve V13 to the independent position 84. In the release position 89, the communication between the supply oil passage 93 and the pilot oil passage 94 is released (the communication is shut off), and the pilot oil passage 94 is in communication with the tank T1. Therefore, at the release position 89, the switching pressure (pilot oil) from the supply oil passage 93 is not output (since the pilot pressure does not act on the pressure receiving portion 95), the first switching valve V13 is at the joining position 83. . Further, at the switching position 90, the supply oil passage 93 is connected to the pilot oil passage 94. Therefore, at the release position 89, the switching pressure from the supply oil passage 93 is output to the pilot oil passage 94. As a result, the switching pressure acts on the pressure receiving portion 95, and the first switching valve V13 is switched to the independent position 84.

That is, the second switching valve V20 has a switching position 90 for outputting a switching pressure for switching the first switching valve V13 from the joining position to the independent position 84, and a release position 89 for not outputting the switching pressure.
The second switching valve V20 has a pressure receiving portion 96 and a pressure receiving portion 97. One end of a pilot oil passage 98 is connected to the pressure receiving portion 96, and one end of the pilot oil passage 99 is connected to the pressure receiving portion 97. As shown in FIG. 3, the other end of the pilot oil passage 98 is connected to the first detection oil passage 100 at an end block B1. One end of the first detection oil passage 100 is connected to the input port 20. In addition, the first detection oil passage 100 is provided from the end block B1 to the control valve V4. Further, the first detection oil passage 100 is provided to pass through the direction switching valve D1, the direction switching valve D2, the direction switching valve D3, and the direction switching valve D4. The other end of the first detection oil passage 100 is connected to the drain oil passage 60 via the oil passage 102 at the control valve V4.

  As shown in FIG. 4, the other end of the pilot oil passage 99 is connected to the second detection oil passage 101 at the end block B2. Further, the second detection oil passage 101 is provided from the end block B2 to the control valve V4. The second detection oil passage 101 is provided passing through the direction switching valve D11, the direction switching valve D10, the direction switching valve D9, the direction switching valve D8, the direction switching valve D7, the direction switching valve D6, and the direction switching valve D5. ing. The other end of the second detection oil passage 101 is connected to the other end of the first detection oil passage 100 by the control valve V4 and is connected to the drain oil passage 60 via the oil passage 102.

When all direction switching valves D1 to D11 are in the neutral position (when all direction switching valves D1 to D11 are not operated), the first detection oil passage 100, the second detection oil passage 101, and the pilot oil passage No pilot pressure is generated at 98 and pilot oil passage 99. In this case, the second switching valve V20 is at the release position 89, and the first switching valve V13 is at the joining position 83 (see FIG. 5).
When at least one of the direction switching valves D1 to D4 (the dozer device 7, the first travel device 3L, and the second travel device 3R) is operated from this state, the middle part of the first detection oil passage 100 is blocked. Ru. As a result, a pilot pressure is generated in the pilot oil passage 98, and the second switching valve V20 is switched to the switching position 90. Then, the pilot pressure acts on the pressure receiving portion 95, and the first switching valve V13 is switched to the independent position 84 (see FIG. 6).

  In a state where the first switching valve V13 is switched to the independent position 84, any one or more of the direction switching valves D5 to 11 (hydraulic attachment, arm 16, bucket 17, boom 15, swivel base 2, swing bracket 14) Is operated, the middle part of the second detection oil passage 101 is shut off. As a result, a pilot pressure is generated in the pilot oil passage 99, and a pilot pressure corresponding to the pilot pressure in the pilot oil passage 98 acts on the pressure receiving portion 97. Then, the second switching valve V20 is switched to the release position 89, and the first switching valve V13 is switched to the joining position 83.

The first switching valve V13 is also at the joining position 83 when one or more of the direction switching valves D5 to D11 are operated without operating the direction switching valves D1 to D4.
As described above, when the hydraulic system drives the work device 4, the first switching valve V13 is at the joining position. In addition, when driving the traveling device 3 without driving the working device 4, when at least one of the first traveling device 3L or the second traveling device 3R is operated, the position is switched to the independent position 84.

It should be noted that the independent position 84 may be set when driving the work device 4 and the merging position 83 may be set when driving the traveling device 3.
<Switching of relief valve setting pressure>
As shown in FIG. 3, FIG. 5, and FIG. 6, one end of the switching oil passage 103 is connected to the pilot oil passage 94. The other end of the switching oil passage 103 is connected to the pressure receiving portion 64 of the first relief valve V21. When the pilot pressure does not act on the pilot oil path 94, the pilot pressure does not act on the switching oil path 103 and the pressure receiving portion 64, so the set pressure of the first relief valve V21 is the first set pressure. When the pilot pressure acts on the pilot oil path 94, the pilot pressure acts on the switching oil path 103 and the pressure receiving portion 64, and the pressure is changed to the second set pressure. That is, the first relief valve V21 is a variable relief valve that is switched to the second set pressure by the switching pressure output from the second switching valve V20.

  As shown in FIG. 5, at the junction position 83, the connection between the second connection oil passage 72 (the second hydraulic oil passage 69) and the relief oil passage 76 is released (one end of the relief oil passage 76 is closed. And the second relief valve V17 does not set the circuit pressure of the second hydraulic fluid passage 69. (The second relief valve V17 does not function as a relief valve that sets the circuit pressure of the second hydraulic fluid passage 69). The first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 communicate with each other, and the first relief valve V21 is provided in the first hydraulic fluid passage 68. Therefore, in this case, the relief valve for setting the circuit pressure of the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 (the circuit pressure of the discharge circuit of the first pump 27) is the first relief valve V21. Further, the set pressure of the first relief valve V21 at this time is a first set pressure. That is, when the work device 4 is driven, the circuit pressure of the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 is the first set pressure of the first relief valve V21. The same applies to driving the swivel base 2, the swing bracket 14 and the hydraulic attachment.

  As shown in FIG. 6, in the independent position 84, the second hydraulic fluid passage 69 is connected to the relief fluid passage 76 via the second connection fluid passage 72 and the communication fluid passage 88. In this case, the second relief valve V17 functions as a relief valve that sets the circuit pressure of the second hydraulic fluid passage 69 (the circuit pressure of the discharge circuit of the second pump port P2). In addition, at the independent position 84, the first relief valve V21 functions as a relief valve that sets the circuit pressure of the first hydraulic fluid passage 68. The set pressure of the first relief valve V21 at this time is a second set pressure higher than the first set pressure. Further, the set pressure of the second relief valve V17 is the same set pressure as the second set pressure. That is, when only the traveling device 3 is driven, the circuit pressure is set with a higher set pressure than when driving the working device 4. The same applies to driving only the dozer device 7 and only the traveling device 3 and the dozer device 7.

As described above, the first relief valve V21 is a relief valve capable of setting the circuit pressure of the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 at the joining position 83 to the first set pressure. The variable relief valve is capable of setting and changing the circuit pressure of the first hydraulic fluid passage 68 to a second set pressure higher than the first set pressure.
In addition, the second relief valve V17 is a relief valve that sets the circuit pressure of the second hydraulic fluid passage 69 to the same set pressure as the second preset pressure at the independent position 84. It is a relief valve that releases the setting of the circuit pressure.

  In the conventional work machine, in addition to the relief valve for driving the work device, the relief valve for the first travel device and the relief valve for the second travel device in order to maintain the traction force of the travel device Is provided. That is, three relief valves are provided. However, since the hydraulic hoses are concentrated around the control valve, there is a demand to make the space of the hose arrangement as wide as possible. In addition, there is also a demand for reducing the number of components and making them inexpensive.

  In this embodiment, when driving the working device 4, the first relief valve V21 functions while the second relief valve V17 does not function, and when driving the traveling devices 3L and 3R without driving the working device 4, the 1 Both the relief valve V21 and the second relief valve V17 function. The first relief valve V21 is used both when driving the working device 4 and when driving the traveling device 3 without driving the working device 4. The set pressure of the first relief valve V21 is changed between when the work device 4 is driven and when the travel device 3 is driven without driving the work device 4. As a result, the number of relief valves can be reduced, and the control valve CV1 can be made compact. By forming the control valve CV1 in a compact size, a wide space for hose arrangement can be taken. Further, by reducing the number of parts, the control valve CV1 can be manufactured inexpensively. In addition, even in the case where working machines having different weights are combined with the hydraulic system, it is possible to secure traveling traction force of the heavy working machines.

  In the illustrated hydraulic circuit, the pilot pressure for switching the first relief valve V21 is taken from the pilot oil passage 94. However, the present invention is not limited to this. When the first switching valve V13 is in the independent position 84, the first relief valve V21 may be changed to the second set pressure. For example, the pilot pressure output from the operation valve V27 for operating the control valve V2 and the operation valve V26 for operating the control valve V3 is applied to the first relief valve V21 to change the set pressure of the first relief valve V21 You may

Further, the set pressure may be electrically switched by the solenoid valve using the first relief valve V21, or the set pressure of the first relief valve V21 may be switched by the pilot pressure from the solenoid valve.
<Return path of return oil of hydraulic actuator>
As shown in FIG. 7, the hydraulic system has a line switching valve V23. The line switching valve V23 is a two-position switching valve that can be switched between the first switching position 109 and the second switching position 110. The first switching position 109 is a position for returning the return oil returned from the hydraulic actuator connected to the control valve V5 to the control valve V5. The first switching position 109 is a position that enables return oil returning from the hydraulic actuator connected to the control valve V5 to return to the tank T1 without passing through the control valve V5.

  A return oil passage (first return oil passage) 111 and a return oil passage (second return oil passage) 112 are connected to the line switching valve V23. The first return oil passage 111 is an oil passage for returning the return oil from the hydraulic actuator to the control valve V5. The second return oil passage 112 is an oil passage for returning the return oil from the hydraulic actuator to the tank T1 without passing through the control valve V5. The second return oil passage 112 is connected to an oil passage 114 connected to the oil discharge port (make-up port) 113 of the swing motor M3. The oil passage 114 is connected to a return oil passage (third return oil passage) 115 and a return oil passage (fourth return oil passage) 116.

The third return oil passage 115 is in communication with the tank T1 via the oil cooler 117. The third return oil passage 115 is provided with a check valve V24. The fourth return oil passage 116 is connected to a tank port 118 provided in the control valve V8, as shown in FIG. The tank port 118 communicates with the drain oil passage 60.
Conventionally, when returning oil from the hydraulic actuator is returned to the tank T1 without passing through the control valve V5, it is returned directly to the tank T1. If so, the heat balance may be deteriorated. Therefore, when returning oil from the hydraulic actuator is returned to the tank T1 without passing through the control valve V5, deterioration of the heat balance can be prevented by returning it to the tank T1 through the oil cooler 117.

  Further, by connecting the second return oil passage 112 to the swing motor M3, the hydraulic hose constituting the second return oil passage 112 can be passed through a wide space between the swing motor M3 and the control valve CV1. Thus, when the breaker or the like is used, it is possible to prevent the hydraulic hose from contacting and damaging the surrounding area by the pulsation and vibration of the hydraulic hose.

The selection valve V25 may be provided in the second return oil passage 112. The selection valve V25 has a first position 119 for flowing the return oil of the hydraulic actuator to the third return oil passage 115 and a second position 120 for returning the return oil of the hydraulic actuator directly to the tank T1 (without passing through the oil cooler 117). It is a 2 position switching valve that can be switched to.
ブ レ ー キ Brake release circuit of swing brake》
As shown in FIG. 7, the hydraulic system has a brake release circuit 121. The brake release circuit 121 is a circuit that outputs a pilot pressure for releasing the swing brake 122 provided to the swing motor M3 to the brake switching valve V28.

  The turning brake 122 is a negative brake, and includes a brake disk 123, a brake cylinder (hydraulic cylinder) 124, and a brake spring 125. The brake disc 123 is provided integrally rotatably with the output shaft 126 of the turning motor M3. The brake cylinder 124 pushes the brake disc 123 by being extended to brake the turning motor M3. The brake cylinder 124 contracts to release the pressure on the brake disk 123 and release the braking of the swing motor M3. The brake spring 125 is incorporated in the brake cylinder 124 and biases the brake cylinder 124 in the extension direction. The brake cylinder 124 is contracted by oil pressure.

  The brake switching valve V28 has a port 127, a port 128, and a port 129. As shown in FIG. 1, the port 127 is connected to the output port 32 via the supply oil passage 130, the supply oil passage 40, and the supply oil passage 38. Therefore, the pilot pressure (pilot oil) discharged from the second pump 28 is supplied to the port 127. The port 128 communicates with the rod side of the brake cylinder 124 (the side opposite to the side where the spring 125 is provided). The port 129 is in communication with the tank T1.

  The brake switching valve V28 has a braking position 131 and a release position 132. The braking position 131 is a position for connecting the port 128 and the port 129 and removing the hydraulic pressure from the brake cylinder 124. That is, it is a position to operate the turning brake 122. The release position 132 is a position where the port 127 and the port 128 are connected to supply the hydraulic pressure to the brake cylinder 124. That is, it is a position at which the turning brake 122 is released.

  The turning brake 122 has a delay function of maintaining the brake released state for several seconds when the brake released state is changed to the brake applied state. This delay function is constituted, for example, by a throttle 162 provided in the flow path for removing the hydraulic pressure from the brake cylinder 124 at the braking position 131. According to this, when the brake switching valve V28 is switched from the release position 132 to the braking position 131 (when the swing brake 122 is put into the operation state from the release state), the pressure release from the brake cylinder 124 is delayed by the diaphragm 162. By this, the brake release state is maintained for several seconds.

Further, the brake switching valve V28 is biased in a direction to be switched to the braking position 131 by the spring 133, and is switched to the release position 132 by the pilot pressure acting on the pressure receiving port 134.
The brake release circuit 121 has one output port 135, five input ports 136 to 140, and four shuttle valves V30 to 33. The output port 135 is connected to the pressure receiving port 134 via the pilot oil passage 140. The pilot pressure from the remote control valve (operation device) 141 is input to the input ports 136 to 139. The pilot pressure from the remote control valve (operation device) 152 is input to the input port 140.

  The remote control valve 141 is a device for operating the control valve V9 (the swivel base 2) and the control valve V6 (the arm 16). The remote control valve 141 has an operation lever 141A. When the control lever 141A is pivoted forward, a pilot pressure is output to the control valve V6 so that the arm 16 performs a dumping operation (pivoting in a direction away from the turntable 2 or upward). When the control lever 141A is rocked later, the pilot pressure is output to the control valve V6 via the pilot oil passage 142 so that the arm 16 performs a cloud movement (swing in the direction approaching the swivel base 2 or downward). When the control lever 141A swings to the right, the pilot pressure is output to the control valve V9 via the pilot oil passage 144 so that the swivel base 2 turns to the right. When the control lever 141A pivots to the left, the pilot pressure is output to the control valve V6 via the pilot oil passage 146 so that the swivel base 2 pivots to the left.

The input port 136 is connected to the pilot oil passage 142 via the pilot oil passage 143. The input port 137 is connected to the pilot oil passage 144 via the pilot oil passage 145. The input port 138 is connected to the pilot oil passage 146 via the pilot oil passage 147.
The remote control valve 152 is a device for operating the control valve V11 (swing bracket 14). The remote control valve 152 has an operation lever 152A. When the control lever 152A swings to the right, the pilot pressure is output to the control valve V11 via the pilot oil passage 148 so that the swing bracket 14 swings to the right. When the control lever 152A swings to the left, the pilot pressure is output to the control valve V11 via the pilot oil passage 150 so that the swing bracket 142 swings to the left.

The input port 139 is connected to the pilot oil passage 148 via the pilot oil passage 149. The input port 140 is connected to the pilot oil passage 150 via the pilot oil passage 151.
Shuttle valves V30 to V33 have two input ports and one output port, and output the pilot pressure on the higher side of the pilot pressure input from the input port from the output port (in the case of the same pressure, Hydraulic fluid is output from the open input port).

  One input port of the shuttle valve V30 is connected to the input port 136 via a pilot oil passage 153. The other input port of the shuttle valve V30 is connected to the output port of the shuttle valve V31 via a pilot oil passage 156. The output port of the shuttle valve V30 is connected to one input port of the shuttle valve V33 via a pilot oil passage 157. One input port of the shuttle valve V 31 is connected to the input port 137 via a pilot oil passage 154. The other input port of the shuttle valve 31 is connected to an input port 138 via a pilot oil passage 155. One input port of the shuttle valve 32 is connected to the input port 139 via a pilot oil passage 158. The other input port of the shuttle valve 32 is connected to the input port 140 via a pilot oil passage 159. The output port of the shuttle valve 32 is connected to the other input port of the shuttle valve V33 via a pilot oil passage 160.

From the above, when the swing operation of the swing base 2, the cloud operation of the arm 16 and the swing operation of the swing bracket 14 are not performed, the swing brake 122 is actuated. When one or more of the swing operation of the swing base 2, the swing operation of the swing bracket 14, and the cloud operation of the arm 16 are performed, the swing brake 122 is released.
The slewing bearing 8 has an outer race fixed to the frame of the traveling device 3 and an inner race fixed to the swivel base 2, and an internal gear is formed on the inner circumferential surface of the inner race. The pivoting motor M3 has a pinion that meshes with the internal gear of the pivoting bearing 8, and pivots the pivot base 2 by driving the pinion.

  When swinging the swing bracket 14, when the swing brake 122 is in operation, a force is applied to the meshing portion between the internal gear and the pinion. In this embodiment, when the swing bracket 14 is operated, the force applied to the meshing portion between the internal gear and the pinion can be released by releasing the swing brake 122. In addition, the work device 4 is provided to be offset to one side (right side) from the center of the swivel base 2. As a result, even when the arm 16 is subjected to a cloud operation (slipping operation), a force is applied to the meshing portion between the internal gear and the pinion when the turning brake 122 is in the operating state. I am trying to do it.

In addition, when the swing bracket 14 is operated, a large inertial force is generated (for example, when soil is piled on the bucket 17 or when the boom 15 and the arm 16 are extended forward) When the swing brake 122 is in the operating state when the swing bracket 14 is suddenly stopped swinging, a large force is applied to the meshing portion between the internal gear and the pinion. Also in this case, the force applied to the meshing portion between the internal gear and the pinion can be released. That is, when the operation of the swing bracket 14 is stopped, the swing brake 122 tries to switch from the released state to the actuated state, but when the swing brake 122 switches from the released state to the actuated state, the swing brake 122 is released for several seconds As a result, the force applied to the meshing portion between the internal gear and the pinion can be released.
<Function effect>
The hydraulic system of the working machine according to the present embodiment includes first control valves V1 and V2 controlling hydraulic actuators, second control valves V3 to V11 controlling hydraulic actuators, a tank T1 storing hydraulic fluid, and hydraulic fluid A first hydraulic oil passage 68 capable of supplying the first control valve V1, V2; a second hydraulic oil passage 69 allowing the hydraulic oil to be supplied to the second control valve V3 to V11; A first transmission oil passage 74 to which the load pressure of the hydraulic actuator controlled by V2 is transmitted, and a second transmission oil passage 75 to which the load pressure of the hydraulic actuator controlled by the second control valves V3 to V11 is transmitted; A junction position 83 communicating the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 and communicating the first transmission fluid passage 74 and the second transmission fluid passage 75, and the first hydraulic fluid passage 68 and the second actuation Disconnecting the communication with the oil passage 69, and 2) The first switching valve V13 which can be switched to the independent position 84 for releasing the communication with the transmission oil passage 75, and the first transmission oil passage 74 at the independent position 84 are connected to the hydraulic oil of the first transmission oil passage 74 The first return circuit 66 is a circuit for returning to the tank T1 and the connection with the first transmission oil passage 74 is released at the joining position 83, and the hydraulic oil of the second transmission oil passage 75 at the joining position 83 and the independent position 84. And a second return circuit 67 for returning the tank T1 to the tank T1.

  As a result, since the first return circuit 66 is disconnected from the first transmission oil passage 74 at the joining position 83, when the first transmission oil passage 74 and the second transmission oil passage 75 are connected, Only the second return circuit 67 functions as a return circuit for returning the hydraulic oil of the first transmission oil passage 74 and the second transmission oil passage 75 to the tank T1. Therefore, the load pressure in the first transmission oil passage 74 and the second transmission oil passage 75 is well boosted without excessively returning the hydraulic oil of the first transmission oil passage 74 and the second transmission oil passage 75 to the tank T1.

  Further, a first pump port P1 discharging hydraulic fluid to the first hydraulic fluid passage, a second pump port P2 discharging hydraulic fluid to the second hydraulic fluid passage, and the first pump port or the second pump A control unit configured to control the flow rate of hydraulic fluid discharged from the first pump port and the second pump port based on the discharge pressure of the port and the load pressure of the first transmission oil passage or the second transmission oil passage; You may have. As a result, since the first return circuit 66 is disconnected from the first transmission oil passage 74 at the joining position 83, when the first transmission oil passage 74 and the second transmission oil passage 75 are connected, Only the second return circuit 67 functions as a return circuit for returning the hydraulic oil of the first transmission oil passage 74 and the second transmission oil passage 75 to the tank T1. Therefore, the load pressure in the first transmission oil passage 74 and the second transmission oil passage 75 is well boosted without excessively returning the hydraulic oil of the first transmission oil passage 74 and the second transmission oil passage 75 to the tank T1. When the first transmission oil passage 74 and the second transmission oil passage 75 are connected by the load pressure in the first transmission oil passage 74 and the second transmission oil passage 75 rising up favorably, the first pump Flow control of hydraulic oil discharged from the port P1 and the second pump port P2 can be performed well.

Further, by providing the first return circuit 66 in the first switching valve V13, the hydraulic system (hydraulic circuit) can be simplified.
The first return circuit 66 connects the first transmission oil passage 74 and the oil discharge passage 77 at the independent position 84, and the first transmission oil at the joining position 83. A connection oil passage 66A for releasing the connection between the passage 74 and the oil discharge passage 77, and a throttle 66B interposed in the connection oil passage 66A. Thus, the first return circuit 66 can be easily configured, and the hydraulic system (hydraulic circuit) can be simplified.

  In addition, a working device 4 having a boom cylinder C3 for driving the boom 15, an arm cylinder C4 for driving the arm 16, and a working tool cylinder C5 for driving the working tool 17, and a first traveling motor M1 A traveling device 3 having a first traveling device 3L and a second traveling device 3R driven by a second traveling motor M2, a boom valve V8 for controlling a boom cylinder C3, and an arm valve V6 for controlling an arm cylinder C4; A first control valve V1, which includes a work valve V7 for controlling a work tool, a first travel valve V2 for controlling a first travel motor M1, and a second travel valve V3 for controlling a second travel motor M2. V2 includes the first travel valve V2, the second control valves V3 to V11 include the second travel valve V3, the boom valve V8, the arm valve V6, and the work implement valve V7, the first control valves V1 and V2 and 2) It is included in any of the control valves V3 to V11 and is switched to the joining position 83 when operating at least one of the boom valve V8, the arm valve V6, and the work implement valve V7, and does not drive the work device 4 When driving 3, at least one of the first travel valve V2 or the second travel valve V3 is switched to the independent position 84. As a result, the load pressure in the first transmission oil passage 74 and the second transmission oil passage 75 is satisfactorily boosted during the operation. Therefore, at the time of operation, the flow rate control of the hydraulic oil discharged from the first pump port P1 and the second pump port P2 can be favorably performed, and the workability can be secured.

  The relief valve sets the circuit pressure of the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 at the joining position 83 to the first set pressure, and the circuit pressure of the first hydraulic fluid passage 68 at the independent position 84 The first relief valve V21 that can be set and changed to a second set pressure higher than the first set pressure, and the relief valve that sets the circuit pressure of the second hydraulic fluid passage 69 at the independent position 84 to the same set pressure as the second set pressure And the second relief valve V17 for releasing the setting of the circuit pressure of the second hydraulic fluid passage 69 at the joining position 83. Thereby, the relief valve for setting the circuit pressure of the first hydraulic fluid passage 68 and the second hydraulic fluid passage 69 at the joining position 83 and the circuit pressure of the first hydraulic fluid passage 68 at the independent position 84 Can also be used as a relief valve to set the number of relief valves.

  The first relief valve V21 further includes a second switching valve having a switching position 90 for outputting a switching pressure for switching the first switching valve V13 from the merging position 83 to the independent position 84 and a release position 89 for not outputting the switching pressure. Is a variable relief valve that is switched to the second set pressure by the switching pressure output from the second switching valve. A hydraulic system (hydraulic circuit) can be simplified by using the switching pressure output from the second switching valve as a pressure for switching the first relief valve V21 to the second set pressure.

  In addition, a relief oil passage 76 in which the second relief valve V17 is interposed is provided, and the first switching valve V13 communicates the second hydraulic fluid passage 69 with the relief fluid passage 76 at the independent position 84 and And a communication oil passage 88 for releasing the communication between the second hydraulic oil passage 69 and the relief oil passage 76. In other words, the communication oil passage 88 is provided in the first switching valve V13, and the communication oil passage 88 is configured to switch the second relief valve V17 between the use state and the non-use state. Thus, the hydraulic system (hydraulic circuit) can be simplified.

  In the hydraulic system of the working machine according to the present embodiment, a tank T1 for storing hydraulic fluid, a hydraulic actuator C1, and a plurality of pilot pressure switching valves D1 and D4 for controlling the hydraulic actuator C1 driven by hydraulic fluid; An operating device 56 capable of operating the plurality of pilot pressure switching valves D1, D4 with hydraulic fluid, and a circuit for returning part of the hydraulic oil for operating the plurality of pilot pressure switching valves D1, D4 to the tank T1 And a common air vent circuit 59 for the pilot pressure switching valves D1, D4. As a result, the amount of leakage of pilot oil from the air removal circuit 59 can be made appropriate, and the pilot circuit 53 supplying hydraulic fluid to the plurality of pilot pressure switching valves D1, D4 can be sufficiently boosted. . As a result, the stability of the operation of the hydraulic actuator C1 can be improved.

Further, the air vent circuit 59 is provided for the pilot pressure switching valve D4 on the downstream side of the hydraulic oil flow path for flowing the hydraulic oil supplied from the operating device 56 among the plurality of pilot pressure switching valves D1, D4. There is. Thus, the air present on the upstream side in the hydraulic oil flow path in which the hydraulic oil supplied from the operation device 56 flows can be well removed. That is, air can be satisfactorily removed (air release can be ensured).
Further, the plurality of pilot pressure switching valves D1, D4 include a first pilot pressure switching valve D1 and a second pilot pressure switching valve D4, and the air vent circuit 59 is a first pilot pressure switching valve D1 or a second pilot. It is provided on one side of the pressure switching valve D4. As a result, the amount of leakage of pilot oil from the air removal circuit 59 can be made appropriate, and the pilot circuit 53 for supplying hydraulic oil to the first pilot pressure switching valve D1 and the second pilot switching valve D4 can be sufficiently It can be boosted. As a result, the stability of the operation of the hydraulic actuator C1 can be improved.

  Also, a first supply circuit 54 for supplying hydraulic fluid from the operation device 56 to one of the first pilot pressure switching valve D1 and the second pilot pressure switching valve D4, and the first pilot pressure switching valve D1 or The air vent circuit 59 is connected to the second supply circuit 55. The pilot circuit 53 has a second supply circuit 55 for supplying hydraulic oil to the other of the second pilot pressure switching valve D4. As a result, the air present in the upstream first supply circuit 54 in the pilot circuit 53 can be well removed.

The hydraulic actuator C 1 is a dozer cylinder that drives the dozer device 7. Thereby, the stability of the operation of the dozer device 7 can be improved.
Although the present invention has been described above, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by claims, and is intended to include all modifications within the meaning and scope equivalent to claims.

DESCRIPTION OF SYMBOLS 4 work apparatus 3 traveling apparatus 3L 1st traveling apparatus 3R 2nd traveling apparatus 15 boom 16 arms 17 work tools (bucket)
29 control unit 66 first return circuit,
67 second return circuit,
68 first hydraulic fluid passage 69 second hydraulic fluid passage 74 first transmission fluid passage 75 second transmission fluid passage 83 joining position 84 independent position 76 relief fluid passage 77 drain fluid passage 66A connection fluid passage 66B throttle 88 fluid passage 89 released Position 90 Switching position C1 Dozer cylinder (hydraulic actuator)
C2 Swing cylinder (hydraulic actuator)
C3 Boom cylinder (hydraulic actuator)
C4 arm cylinder (hydraulic actuator)
C5 Workpiece cylinder (hydraulic actuator)
M1 1st traveling motor (hydraulic actuator)
M2 2nd traveling motor (hydraulic actuator)
M3 Swing motor (hydraulic actuator)
P1 1st pump port P2 2nd pump port T1 tank V1 1st control valve (1st dozer valve)
V2 1st control valve (1st travel valve)
V3 2nd control valve (2nd travel valve)
V4 2nd control valve (2nd dozer valve)
V5 2nd control valve (1st spare valve)
V6 2nd control valve (arm valve)
V7 2nd control valve (workpiece valve)
V8 2nd control valve (boom valve)
V9 2nd control valve (turning valve)
V10 2nd control valve (2nd spare valve)
V11 2nd control valve (swing valve)
V13 1st switching valve V17 2nd relief valve V20 2nd switching valve V21 1st relief valve

Claims (8)

A first control valve that controls the hydraulic actuator;
A second control valve that controls the hydraulic actuator;
A tank for storing hydraulic oil,
A first hydraulic oil passage capable of supplying hydraulic oil to the first control valve;
A second hydraulic oil passage capable of supplying hydraulic oil to the second control valve;
A first transmission oil passage to which a load pressure of a hydraulic actuator controlled by the first control valve is transmitted;
A second transmission oil passage to which a load pressure of a hydraulic actuator controlled by the second control valve is transmitted;
A junction position in which the first hydraulic fluid passage is communicated with the second hydraulic fluid passage and the first transmission fluid passage is communicated with the second transmission fluid passage, the first hydraulic fluid passage and the second actuation. A first switching valve switchable to an independent position for releasing the communication with the oil passage and releasing the communication between the first transmission oil passage and the second transmission oil passage;
The circuit is connected to the first transmission oil passage at the independent position to return the hydraulic oil of the first transmission oil passage to the tank, and the connection with the first transmission oil passage is released at the joining position. First return circuit,
A second return circuit for returning hydraulic oil of the second transmission oil passage to the tank at the joining position and the independent position;
The hydraulic system of the working machine that is equipped with. A first pump port for discharging hydraulic fluid to the first hydraulic fluid passage;
A second pump port for discharging hydraulic fluid to the second hydraulic fluid passage;
Operation of discharging from the first pump port and the second pump port based on the discharge pressure of the first pump port or the second pump port and the load pressure of the first transmission oil passage or the second transmission oil passage A control unit that controls the flow rate of oil;
The hydraulic system of the working machine according to claim 1, comprising:   The hydraulic system of a working machine according to claim 1 or 2, wherein the first return circuit is provided to the first switching valve. An oil discharge passage communicating with the tank;
The first return circuit is
A connection oil passage which connects the first transmission oil passage and the oil discharge passage at the independent position, and releases the connection between the first transmission oil passage and the oil discharge passage at the joining position;
The hydraulic system of the working machine according to any one of claims 1 to 3, further comprising: a throttle interposed in the connection oil passage. A working device having a boom cylinder for driving the boom, an arm cylinder for driving the arm, and a working tool cylinder for driving the working tool;
A traveling device having a first traveling device driven by a first traveling motor and a second traveling device driven by a second traveling motor.
A boom valve for controlling the boom cylinder;
An arm valve for controlling the arm cylinder;
A tool valve for controlling the tool;
A first travel valve that controls the first travel motor;
A second travel valve that controls the second travel motor;
Equipped with
The first control valve includes a first travel valve,
The second control valve includes a second travel valve,
The boom valve, the arm valve, and the work implement valve are included in any of the first control valve and the second control valve,
Switching to the merging position when operating at least one of the boom valve, the arm valve, and the work tool valve;
5. The driving apparatus according to claim 1, wherein the driving device is switched to the independent position when operating at least one of the first travel valve and the second travel valve when driving the traveling device without driving the working device. The hydraulic system of the work machine according to any one of the items. A relief valve for setting the circuit pressure of the first hydraulic fluid passage and the second hydraulic fluid passage to a first set pressure at the joining position, the circuit pressure of the first hydraulic fluid passage being at the independent position; 1st relief valve which can be set and changed to the 2nd setting pressure higher than 1 setting pressure,
A relief valve which sets the circuit pressure of the second hydraulic fluid passage to the same set pressure as the second set pressure at the independent position, and cancels the setting of the circuit pressure of the second hydraulic fluid passage at the merging position A second relief valve,
The hydraulic system of the working machine according to any one of claims 1 to 5, comprising: A second switching valve having a switching position for outputting a switching pressure for switching the first switching valve from the joining position to the independent position, and a release position for not outputting the switching pressure;
The hydraulic system according to claim 6, wherein the first relief valve is a variable relief valve that is switched to the second set pressure by the switching pressure output from the second switching valve. A relief oil passage provided with the second relief valve;
The first switching valve communicates the second hydraulic fluid passage with the relief fluid passage at the independent position, and releases the communication between the second hydraulic fluid passage and the relief fluid passage at the joining position. The hydraulic system of the working machine according to claim 6 or 7, further comprising a communicating oil passage.